Elongated medical instruments are inserted into a patient's body to perform a wide variety of procedures. Catheters, for example, are often inserted into a subject to drain fluids, or used to deliver and implant a medical device, such as a stent or a prosthetic valve, at a location inside a subject. Cardiac catheterization, such as for performing angioplasty or implanting a prosthetic heart valve, can involve the use of a relatively long catheter that is advanced through a patient's vasculature to access the heart. In one approach, for example, the catheter can be advanced through a femoral artery and the aorta to access the heart.
Control and advancement of catheters, especially for cardiac catheterization, is difficult because of their construction. The user must frequently manipulate, or torque, the catheter shaft on the proximal end to facilitate advancement of the catheter with a desired orientation on the distal end. To provide the needed control over the movement of the catheter, it is necessary that these tubular catheters be made somewhat rigid. However, catheters must be flexible enough to navigate through the body lumen to arrive at the desired location within the body where the medical procedures will be performed. An overly rigid catheter shaft will not easily track, or follow, a guidewire. Because of their length, it is often necessary for the practitioner to grasp the relatively narrow shaft of the catheter at a location near the entry point into the patient's vasculature rather than the handle at the very proximal end of the catheter to avoid buckling of the shaft. Unfortunately, it is often difficult to obtain and maintain a sure grip on the relatively narrow shaft for the necessary control and grasping the shaft with a tight grip causes user fatigue.
Therefore, what has been needed is a device that improves a practitioner's ability to insert and control advancement of a medical instrument through a patient's body.